Compositions and methods for polishing (e.g., planarizing) the surface of a substrate are well known in the art. Polishing compositions (also known as polishing slurries) typically contain an abrasive material in an aqueous solution and are applied to a surface by contacting the surface with a polishing pad saturated with the polishing composition. Typical abrasive materials include silicon dioxide, cerium oxide, aluminum oxide, zirconium oxide, and tin oxide. U.S. Pat. No. 5,527,423, for example, describes a method for chemically-mechanically polishing (CMP) a metal layer by contacting the surface with a polishing composition comprising high purity fine metal oxide particles in an aqueous medium. The polishing composition is typically used in conjunction with a polishing pad (e.g., polishing cloth or disk). Suitable polishing pads are described in U.S. Pat. Nos. 6,062,968, 6,117,000, and 6,126,532, which disclose the use of sintered polyurethane polishing pads having an open-celled porous network, and U.S. Pat. No. 5,489,233, which discloses the use of solid polishing pads having a surface texture or pattern. Alternatively, the abrasive material may be incorporated into the polishing pad. U.S. Pat. No. 5,958,794 discloses a fixed abrasive polishing pad.
The chemical additives in polishing compositions play an important role in the polishing of substrates. While chemical additives can increase the removal rate of substrate material in polishing a substrate's surface, the chemical additives can adversely affect surface planarity and corrosion of the substrate. Therefore, it is desirable to formulate polishing compositions that can rapidly polish substrate surfaces without significantly adversely affecting the surface planarity or corrosion of the substrate.
Polymers are one type of chemical additive that has been used as a component of polishing compositions. Polymers can serve in various roles in the polishing compositions such as surfactants or polyelectrolytes (see, for example, U.S. Pat. Nos. 5,264,010, 5,860,848, 5,958,794, 6,303,049, and 6,348,076 and EP 0919602). For instance, U.S. Pat. No. 5,352,277 discloses a polishing composition, for polishing silicon wafers used in integrated circuits, comprising water, silica, a water-soluble salt, and a water-soluble polymer. The water-soluble polymer can be polyethylene oxide, polyacrylamide, polyvinyl pyrrolidone, poly(meth)acrylic acid, or polymaleic acid. In addition, U.S. Pat. No. 4,983,650 describes polishing compositions for polishing wafers comprising water, silica, and a polysaccharide graft-polymerized with acrylamide alone or together with at least one vinyl monomer (e.g., (meth)acrylic acid, styrenesulfonic acid). EP 0840664 discloses a polishing composition for silicon wafers comprising water, silica, salt, an amine compound, and a polyelectrolyte dispersion (e.g., polyvinyl alcohol, polyethylene oxide).
A need remains, however, for polishing systems and polishing methods that will exhibit desirable planarization efficiency, selectivity, uniformity, and removal rate during the polishing and planarization of substrates, in particular metal substrates, while minimizing defectivity, such as surface imperfections and damage to underlying structures and topography during polishing and planarization.
The invention seeks to provide such a polishing system and method. These and other advantages of the invention will be apparent from the description of the invention provided herein.